For example, a provider that provides users with services (hereinafter simply referred to as a provider as well) constructs and operates a job system (hereinafter referred to as information processing system as well) corresponding to applications in order to provide the users with various services. Specifically, the provider constructs an information processing system functioning as the Internet of things (IoT) system in order to, for example, analyze various data in a data center (temperature, humidity, and the like in the data center).
Such an information processing system includes, for example, a plurality of sensors (hereinafter referred to as sensor devices as well) that measure various data in the data center and a device (hereinafter referred to as information collection device as well) that collects and accumulates the data transmitted from the sensor devices. The information processing system as described above includes a device (hereinafter referred to as information analysis device as well) that acquires data accumulated in the information collection device and analyzes the acquired data.
The sensor devices included in the information processing system encrypt data to be transmitted (the data encrypted by the sensor devices is hereinafter referred to as encrypted data as well) when the sensor devices transmit data to the information collection device. When the information collection device included in the information processing system receives the encrypted data transmitted from the sensor devices, the information collection device decrypts the encrypted data and accumulates the decrypted data in a storing section. Consequently, the provider is capable of securing security of the data transmitted from the sensor devices to the information collection device (see, for example, Japanese Laid-open Patent Publication Nos. 2008-160520, 2008-124824, and 2000-138916).
When the sensor devices encrypt data to be transmitted to the information collection device, for example, every time the sensor devices transmit the encrypted data to the information collection device, the sensor devices transmit information for decrypting the encrypted data (the information hereinafter simply referred to as keys as well). Specifically, for example, upon receipt of notification that the encrypted data are received, from the information collection device, the sensor devices transmit keys for decrypting the encrypted data received by the information collection device.
However, when a large number of encrypted data are transmitted by the sensor devices (the encrypted data are transmitted a large number of times), the number of keys to be transmitted to the information collection device increases. Accordingly, in the information processing system described above, communication cost for decrypting the encrypted data is sometimes enormous depending on, for example, the number of encrypted data transmitted by the sensor devices.